The present invention relates generally to fabrication of solid state electronic devices, and more specifically to such fabrication which controls the formation of crystalline defects in such devices.
Experience has shown a need to control minority carrier lifetime in various solid state devices, including heterojunction bipolar transistors (HBTs). For example, it would be beneficial to produce HBT devices that have consistent current gain so that the circuit yield is high.
The prior art taught that the introduction of impurities, such as Au, into a high-speed diode can adjust the minority carrier lifetime. Prior HBTs use any of the following: graded, narrow, doped, or stepped base regions to adjust where the minority carriers will recombine. This invention addresses the problems presented by the foregoing prior art and provides a solution.
Applicant has discovered a method of fabricating a solid state electronic device which is believed capable of controlling minority carrier lifetime. According to one embodiment, the device comprises a substrate and layers. The one embodiment introduces introduces crystalline defects in at least one of the layers and controls the densities in at least the one layer, whereby at least one characteristic of the device is controlled. For example, the current gain beta of the device can be controlled. The crystalline defect densities may be controlled by controlling the temperature of the substrate.
By using the method, the characteristics of a solid state electronic device can be controlled with a degree of ease and accuracy previously unattainable. For example, the one embodiment allows an engineer an additional in-process method to control where the minority carriers will recombine to achieve the desired current gain beta.